Evolutionarily conserved DELLA-mediated gibberellin signaling in plants.

Gibberellins (GAs) play important roles in many essential plant growth and development processes. A family of nuclear growth-repressing DELLA proteins is the key component in GA signaling. GA perception is mediated by GID1, and the key event of GA signaling is the degradation of DELLA proteins via the 26S proteasome pathway. DELLA proteins integrating other plant hormones signaling and environmental cue modulating plant growth and development have been revealed. GA turning on the de-DELLA-repressing system is conserved, and independently establishes step-by-step recruitment of GA-stimulated GID1-DELLA interaction and DELLA growth-repression functions during land plant evolution. These discoveries open new prospects for the understanding of GA action and DELLA-mediated signaling in plants.

An updated GA signaling 'relief of repression' regulatory model.

Gibberellic acid (GA) regulates many aspects of plant growth and development. The DELLA proteins act to restrain plant growth, and GA relieves this repression by promoting their degradation via the 26S proteasome pathway. The elucidation of the crystalline structure of the GA soluble receptor GID1 protein represents an important breakthrough for understanding the way in which GA is perceived and how it induces the destabilization of the DELLA proteins. Recent advances have revealed that the DELLA proteins are involved in protein-protein interactions within various environmental and hormone signaling pathways. In this review, we highlight our current understanding of the 'relief of repression' model that aims to explain the role of GA and the function of the DELLA proteins, incorporating the many aspects of cross-talk shown to exist in the control of plant development and the response to stress.